Cereal Chem 59:533 - 537.  |  VIEW ARTICLE
High-Temperature Short-Time Extrusion Cooking of Wheat Starch and Flour. II. Effect of Protein and Lipid on Extrudate Properties.

J. M. Faubion and R. C. Hoseney. Copyright 1982 by the American Association of Cereal Chemists, Inc. 

The role of lipid and protein in the extrusion cooking of wheat starch and flour was studied. Effects caused by protein depended on protein type and concentration. When added to wheat starch at concentrations up to 11%, wheat gluten reduced expansion and texture. The ultrastructure of starch-plus-gluten extrudates changed gradually from starchlike to flourlike as gluten content increased. A specific gluten concentration could not be identified as the border between starchlike and flourlike structures. At equivalent concentrations, soy protein isolate increased expansion and texture. Textural measures increased even after expansion began to decrease at the highest soy concentration tested. At and above 5% soy protein isolate, starch extruded to produce ultrastructures different from both starch and flour. Removing free-flour lipids increased extruded flour texture and expansion. Adding flour lipids to all materials tested resulted in decreased extrudate expansion and texture. The magnitude of the changes depended on the material extruded. Changes in ultrastructure caused by adding or removing lipids were subtle and did not always reflect expansion and textural changes observed in the same sample.